Creep Ratio of Thermoplastic Pipes
ISO 9967
After installation, underground pipes are subject to an extensive constant pressure load. Creep tests on plastic pipes are used to determine the long-term behavior of pipe sections under radial loading or using a flexure assembly, usually for a test duration of 42 days. Results, for example include creep behavior (creep) and creep modulus.
Objective & running a test Other standards Testing systems Plastics brochure
Objective and performance of the creep test to ISO 9967
- After installation, underground pipes are subject to an extensive constant pressure load. Experience has shown that the increase in deformation is largely completed after a relatively short time.
- The creep behavior test to ISO 9967 is based on the standard for determination of the ring stiffness ISO 9969. Since in practice the deformation is completed after two years at the latest, sufficiently accurate characteristic values can be obtained by measurements over a period of 42 days.
- During the test, a pipe section is loaded by a constant radial force. This force is selected so that there is a deformation of 1.5% of the ring cross section. Under this load, the ring deformation is read at defined intervals. With modern testing machines, however, continuous recording of the ring deformation is also possible today.
- The deformation to be expected after two years is calculated by extrapolating a regression line of the measured values. With ZwickRoell testing machines, this task, as well as the display of the logarithmically scaled deformation-time diagram is assumed by the testXpert III testing software. Interference by the operator during the measurement process is therefore not necessary.
Other standards applicable in this environment
- ISO 899-2 - Plastics - Determination of creep behavior - Part 2: Flexural creep by three-point loading
- ISO 7684 - Glass-reinforced thermosetting plastics (GRP) pipes – Determination of the creep factor under dry conditions
- EN 761 - Glass-reinforced thermosetting plastics (GRP) pipes — Determination of the creep factor under dry conditions
- EN 1862 - Glass-reinforced thermosetting plastics (GRP) pipes – Determination of the relative flexural creep factor following exposure to a chemical environment
